The present invention relates to a solenoid valve of the type having an armature of two generally rod-like parts, of which only one part moves during solenoid energization and de-energization, to open and close a fluid port or path. For extreme sensitivity and quick response, a return bias or spring, the magnetic characteristics and the axial gap between the two parts of the armature have to be carefully and precisely selected. The valve can be the two-port open or shut type, or a 3/2 type where a common port can be connected to one of two others.
A primary object of the valve of the invention is to provide adjustability in the suspension of a vehicle whenever the gravity loading of the vehicle is altered, e.g., from one to five passengers, perhaps with some, or much luggage. Usually it will be set at the beginning of a journey. Alternatively, for use in level setting of a vehicle suspension, quick reaction, sensitivity and repeatability may often be significant, because it is often desirable that the suspension activity respond to road surface to become harder or softer. The valve should be able to be pulsed open and shut rapidly in order to pump a pneumatic suspension up or down e.g., with air at high pressure. If large unknown electrical currents are required, to open the fluid path, whether gas or liquid, or indeed to close a normally open path, rapid responses would not be possible.
It is desirable therefore that the armature gap between the two parts be easy to adjust, but once adjusted manually, to keep its gap adjustment with acceptably improved sensitivity.